fix: prefer MSVC over MinGW for Windows bootstrap

src/installer.test.ts

@@ -2,7 +2,11 @@ import {describe, expect, test, vi, beforeEach, afterEach} from 'vitest'
 import * as fs from 'fs'
 import * as os from 'os'
 import * as path from 'path'
-import {getVExecutable, getWindowsBuildCommand, resolveVersionRef} from './installer'
+import {
+  getVExecutable,
+  getWindowsBuildCommand,
+  resolveVersionRef
+} from './installer'
 import * as githubApiHelper from './github-api-helper'
 
 describe('getVExecutable', () => {
@@ -62,17 +66,30 @@ describe('getWindowsBuildCommand', () => {
     }
   })
 
-  test('prefers makev.bat when present', () => {
+  test('prefers makev.bat when present (MSVC by default)', () => {
     fs.writeFileSync(path.join(tempDir, 'makev.bat'), '@echo off')
     fs.writeFileSync(path.join(tempDir, 'make.bat'), '@echo off')
 
-    expect(getWindowsBuildCommand(tempDir)).toBe('.\\makev.bat -gcc')
+    expect(getWindowsBuildCommand(tempDir)).toBe('.\\makev.bat')
   })
 
-  test('falls back to make.bat for older releases', () => {
+  test('uses makev.bat with -gcc when useGcc is true', () => {
+    fs.writeFileSync(path.join(tempDir, 'makev.bat'), '@echo off')
+    fs.writeFileSync(path.join(tempDir, 'make.bat'), '@echo off')
+
+    expect(getWindowsBuildCommand(tempDir, true)).toBe('.\\makev.bat -gcc')
+  })
+
+  test('falls back to make.bat for older releases (MSVC by default)', () => {
+    fs.writeFileSync(path.join(tempDir, 'make.bat'), '@echo off')
+
+    expect(getWindowsBuildCommand(tempDir)).toBe('.\\make.bat')
+  })
+
+  test('falls back to make.bat with -gcc when useGcc is true', () => {
     fs.writeFileSync(path.join(tempDir, 'make.bat'), '@echo off')
 
-    expect(getWindowsBuildCommand(tempDir)).toBe('.\\make.bat -gcc')
+    expect(getWindowsBuildCommand(tempDir, true)).toBe('.\\make.bat -gcc')
   })
 
   test('throws when no build script exists', () => {

src/installer.ts

@@ -105,29 +105,54 @@ export async function getVlang({
   return installDir
 }
 
-export function getWindowsBuildCommand(installDir: string): string {
+export function getWindowsBuildCommand(
+  installDir: string,
+  useGcc = false
+): string {
+  const gccFlag = useGcc ? ' -gcc' : ''
   if (fs.existsSync(path.join(installDir, 'makev.bat'))) {
-    return '.\\makev.bat -gcc'
+    return `.\\makev.bat${gccFlag}`
   }
   if (fs.existsSync(path.join(installDir, 'make.bat'))) {
-    return '.\\make.bat -gcc'
+    return `.\\make.bat${gccFlag}`
   }
   throw new Error(`No Windows build script found in ${installDir}`)
 }
 
 function buildV(installDir: string): void {
   if (process.platform === 'win32') {
-    const command = getWindowsBuildCommand(installDir)
-    // vlang/v CI builds Windows with .\makev.bat (see windows_ci_gcc.yml).
-    core.info(`Running ${command}...`)
-    // eslint-disable-next-line no-console
-    console.log(
-      execSync(command, {
-        cwd: installDir,
-        shell: process.env.ComSpec ?? 'cmd.exe',
-        stdio: 'pipe'
-      }).toString()
-    )
+    // GHA Windows runners ship MSVC (Visual Studio Build Tools), which
+    // provides the POSIX-compatible headers V needs to bootstrap. MinGW
+    // (-gcc) lacks sys/mman.h, termios.h and pthread types, so try MSVC
+    // first and fall back to GCC only if the MSVC build fails.
+    try {
+      const msvcCommand = getWindowsBuildCommand(installDir, false)
+      core.info(`Running ${msvcCommand} (MSVC)...`)
+      // eslint-disable-next-line no-console
+      console.log(
+        execSync(msvcCommand, {
+          cwd: installDir,
+          shell: process.env.ComSpec ?? 'cmd.exe',
+          stdio: 'pipe'
+        }).toString()
+      )
+    } catch (msvcError) {
+      const msvcMessage =
+        msvcError instanceof Error ? msvcError.message : String(msvcError)
+      core.warning(
+        `MSVC build failed (${msvcMessage}), falling back to GCC (MinGW)...`
+      )
+      const gccCommand = getWindowsBuildCommand(installDir, true)
+      core.info(`Running ${gccCommand} (GCC)...`)
+      // eslint-disable-next-line no-console
+      console.log(
+        execSync(gccCommand, {
+          cwd: installDir,
+          shell: process.env.ComSpec ?? 'cmd.exe',
+          stdio: 'pipe'
+        }).toString()
+      )
+    }
     return
   }